Method of preparing vegetable proteins



Patented Oct. 6, 1942 METHOD OF PREPARING VEGETABLE PROTEINS John 0.Brier and Gerard w. Mulder, Arm Arbor,

Mich, assignor to Welsh and Green, Incorporated, Chicago, Ill., acorporation of Delaware No Drawing.

3 Claim.

This invention relates to vegetable proteins and methods of preparingthe same. More particularly it relates to modified forms of soy beanmeal and like products and to methods of preparing the same. It alsorelates to the insoluble proteinogenous materials contained in suchvegetable products as soy beans, peanuts, other oleaginous seedmaterials, leguminous products and other protein containing vegetablematerials, as well as to methods of isolating, more or less completely,such insoluble proteinogenous materials without efiecting hydrolysis orother changes therein.

The prior art is familiar with materials such as soy bean meal which isthe crushed residue remaining after at least the greater proportion ofoily matter has been removed from soy beans.

Soy bean meal may be further treated physically to produce a more highlypurified proteinogenous material. The co-pending application Serial No.159,069 of the senior co-inventor of the instant application, John C.Brier, filed August 14, 1937, discloses a method of preparing proteinsfrom soy bean meal which comprises mixing the latter with acidulatedwater so that the resulting solution when in equilibrium issubstantially at the isoelectric point of the proteins present andseparating said proteins from the resulting solution. This washingprocess, which of course removes only soluble materials, still leavesthe fibrous and insoluble galactanous materials contained by the soybeans associated with the proteins.

Application March 13, 1939, Serial No. 261,652

These two products, soy bean meal and soy bean washed with acidulatedwater, are mixtures of vegetable proteins substantially unchangedchemically, with other vegetable non-proteinogenous materials. Thelatter product is at present not known to the art.

The prior art is also acquainted with so-called treated vegetableproteins. Those skilled in the art usually understand this term assignifying products that may be derived from soy bean meal or likematerials by selective extraction of proteinogenous materials therefromwith strongly alkaline solutions, from which the proteins arereprecipitated by the addition of acids. Such treated vegetable proteinsare practically free from fibrous and insoluble galactanous materialsand other non-proteinogenous materials. They do not, however, representthe proteins of the soy bean in the form that they are contained in saidbeans, but are chemically changed products, for during the alkalinetreatment of the soy bean meal the sensitive proteins contained thereinare inevitably hydrolyzed to a greater or lesser extent. Those skilledin the art have been accustomed not only not to avoid such hydrolysisbut to produce it purposely. Cone and Brown, the inventors of theintensive, prolonged alkaline extraction and digestion treatmentdescribed in U. S. Patent 1,955,375 state expressly in lines 77 to 85 onpage 1 of their patent:

The digestion in aqueous solution occasions a denaturing action, besidesmaking possible the elimination of other seed constituents. ln thistreatment the protein becomes dispersible, that is, now capable of beingtaken up in an aqueous menstruum, and its ultimate viscosity may becontrolled.

This statement clearly shows that during the alkaline extractiontreatment the nature of the proteins present is modified; in particular,such modification is evidenced by a change in viscosity. It is moreoverasserted that unless so treated the vegetable proteins are notdispersible in water.

In general it may be said that any method of isolating an approximatelypure vegetable protein comprising a step in which the protein to beisolated is selectively dissolved in alkaline or acid aqueous medianecessarily occasions at least some hydrolysis of the protein. Althoughthe resultant product may be free of non-proteinogenous substances,possibly even homogeneous, and thus entitled to be called pure, it stillwould not represent a pure form of the original protein. It would simplybe a pure, modified protein.

We are not aware of any heretofore known products on the order of acomminuted defatted oleaginous seed material such as soy bean meal,which may or may not have been subjected to a washing with water at a pHapproximately that of the isoelectric point of the protein containedtherein to remove water soluble constituents,

which do not contain substantially all the fibrous and insolublegalactanous material originally present in the oleaginous seeds, or ofany product representing an approximately pure and unchanged form of theprotein as contained in the Another important object of this inventionis to provide a more highly purified unchanged form of the insolubleproteins contained in vegetable materials, particularly with respect tofreedom from fibrous and insoluble galactanous materials.

A further important object of this invention is to provide processescapable of producing these contemplated products.

Other and further important objects of this invention will becomeapparent from the appended description and claims.

In proceeding in accordance with this invention, a modified form of aprotein containing vegetable material is used as starting material. Theoriginal source of the latter may be oleaginous seed material such assoy beans, cotton seed, peanuts, tung nuts, castor beans, linseed,cereals or grains, leguminous products or other suitable vegetablematerial. If oleaginous seed material is used, any dark colored shell orhull may first be removed, if desired, by a suitable method ofdecortication, after which the greater part or all of the oily matterpresent is removed, by extraction with, for instance, hexane, or by anyother means, such as mechanical pressing, whereby a product on the orderof soy bean meal is obtained.

In modifying the product on the order of soy bean meal thus obtained tomake it a suitable raw material for the products and processes disclosedin this application, it is further treated to partially disintegrate itscellular structure and to remove the water soluble constituentstherefrom. The latter include water soluble proteins, in particular,albumin proteins, carbohydrates, hemicelluloses and galactans. Ingeneral our process contemplates a combined washing and steepingtreatment of high protein meal residue obtained by extraction of oilfrom, say, linseed, cotton seed, or soy beans, with acidulated watersuch that the pH of the resultant mixture is at all times approximately,though not necessarily exactly, at the isoelectric point of theinsoluble vegetable protein present. This step differs from the processdisclosed in the co-pending application, Serial No. 159,069, bypermitting the use of pH values varying substantially, although withindefinite limits depending on the particular vegetable material beingtreated, from the isoelectric point of the protein being isolated, andby prolonging the time of treatment from the two hours usually neededfor washing purposes to as much as twenty-five to fifty hours. Thisprolonged steeping causes the cell material to swell, proteinagglomerates to separate, and, in general, the soy bean meal or othermaterial being treated to be rendered softer and made more suitable fora succeeding mechanically disintegrating step.

More particularly, we find that a prolonged leaching of the meal withacidulated water will effect a swelling and softening of the sameaccompanied by a complete extraction of the water soluble proteins,carbohydrates, hemi-celluloses and galactans. The specific acid used forcontrolling the pH may be varied. Acids that may be used includesulfurous, sulfuric, hydrochloric, citric, tartaric, lactic, malic,acetic, succinic, benzoic and others. Sulfurous and hydrochloric acidsare preferable because neither tends to cause discoloration of the mealand both are relatively cheap. Sulfurous acid particularly promotes theswelling of the meal. Generally a pH of between 3.8 and 5.4, andpreferably between 4.0 and 4.9, is used for the isolation of globulin,

size and shapes.

the chief protein present in soy beans, which has an isolectric point of4.4. When hydrochloric acid is used, about 2.8 per cent by weight ofacid,

of 20 B. is usually necessary to eifect a suitable pH in the wash water.This figure, however, is not valid for all soy bean meals, forvariations in the.climatic and soil conditions under which the beanswere grown may cause variations in composition which have to becompensated for.

The extraction of water soluble constituents is promoted by carrying outthis treatment with acidulated water as counter-current leaching or bythe repeated decanting of the supernatant liquid which is then replacedwith fresh acidulated water. We have, for instance, successfully usedfour counter-current washes using a total amount of water abouttwenty-five times the weight of the protein meal being leached, or threesuccessively replaced batches of acidulated water removed by decantationamounting to forty times the weight of the meal.

The residue left after this treatment with acidulated water is the rawmaterial for the products and processes contemplated by this invention.It contains intercellular fiber, insoluble galactans and protein. Iforiginally used beans were not decorticated, the residue will alsocontain hullfiber. The term "fibrous and insoluble, galactanousmaterials as used herein signifies the insoluble non-proteinogenousconstituents of the thus prepared starting material, while the termsoluble constituents refers to the materials capable of being removed bythis leaching with acidulated water.

We have discovered by microscopic observation that when the residue fromthe leaching with acidulated water is subjected to a suitable combinedtearing and abrading treatment in the presence of water, as when it iswet-burred in a manner similar to the wet-burring of corn starch, thefiber and galactans present tend to string out in long fibrils, whereasthe protein agglomerates are broken up andindividual spherical proteinparticles are released. We have further discovered that when it isattempted to cause the paste resulting from the treatment just describedto pass through a suitable screen while water is simultaneously sprayedthereon, the protein particles, being round, pass through the screenwhile fibers and galactanous materials are washed off the screen. Inthis manner it is possible to effect a good separation of proteinogenousand nonproteinogenous materials.

The milling of the sludge left from the leaching with acidulated wateris readily accomplished by one skilled in the art of wet burring, whowill be able to properly adjust the variable factors of this process soas to obtain the desired particle These factors include the amount ofwater used, the size and speed of the mills, the tightness with whichthe burrs are set, the character of the burr mill surfaces and the like.

The time required for milling is reduced materially by carrying out thisstep at an elevated temperature. At F., for instance, the rate ofburring is approximately four times the rate at +70 F.

This milling is most suitably efiected at or around the pH representingthe isoelectric point of the protein being isolated. The addition ofmore acid may be necessary to maintain this acidity.

The exact size, shape and material of construction of the screen usedmay be varied widely. For

laboratory purposes a fiat shaking screen of silk bolting cloth has beenfound suitable, whereas an octagonal rotating trommel of the typepresently used in the starch industry would probably best meet therequirements of commercial plantscale operation. 'The particular meshsize of the screen should be adapted to the grinding conditions used. Wehave successfully used screen mesh sizes varying from 90 to 200 mesh.

Part of the protein may adhere to the fibrous and galactanous material,and reburring and rescreening of the tailings from the first wetscreening may be efiected to obtain a more perfect recovery of proteins.A repetition of the process will after several cycles yield diminishingreturns; the final tailings, after the optimum number of wet screeningshas been accomplished, will still contain some protein and may be driedand sold as cattle feed.

The protein suspension washed through the screen is collected in a tankand the suspended protein is allowed to settle out. This settling isvery rapid and complete if the pH is maintained within the range of theisoelectric point of the protein. A range from pH 4.0 to 4.9 has beenfound suitable for most purposes.

The protein thus thickened by sedimentation may be easily filtered bymeans of standard filtration and equipment such a a plate and framefilter press or a continuous rotary filter. We find that a dense cakecontaining 70% moisture may readily be obtained in a plate and framefilter press using one inch frames and pressures from to 9 pounds persquare inch.

This filter cake may be crushed and dried in any suitable manner. Thedrying should preferably be carried out below 60 C. We have found aconvenient and rapid method of drying this cake in passing it through anextruder to form small strings of wet protein. The surface area of theprotein is thus greatly increased whereby the drying is acceleratedconsiderably.

The dried cake is broken up, for instance, in a hammer or ball mill, andthe granulated product thus formed represents the finished product.

The process disclosed hereinbefore may be applied to the production ofsoy bean protein with excellent results.

The following detailed description of a preferred form of the presentinvention will serve as an example illustrating the working of thisinvention.

Solvent extracted soy bean meal is mixed with water containing sulfurdioxide maintained at about 100 F. Enough sulfur dioxide is added tomaintain the pH of the resulting slurry within the range of from 4.5 to5.0. This slurry is kept at the indicated pH value and temperature for35 hours during which time the supernatant liquid is decanted threetimes and replaced with fresh water, these decantations effectingremoval of soluble carbohydrates, albumins, and other substances. Theratio, by weight, of meal to water used during this combined washing andsteeping treatment is 1 to 40.

After this leaching, the solid content of the slurry is adjusted so asto be one-seventh of the total weight of the slurry. The temperature isthen raised to 120 F. Burring is carried out in a 16-inch burr mill, andscreening, settling, filtration and drying is eilected as disclosedhereinbefore.

It is also within the scope of this invention to utilize the discloseddifferences in particle size, shape and gravity between protein andnon-proteinogenous material to effect separation in any manner capableof effecting such results, such as centrifugal separation, difierentialsettling, with or without washing, mechanical concentration methods onthe order of flotation, and other conventional methods so well known tothe prior art that they need not be discussed.

It can thus be seen that our process is carried out easily andconveniently with standard equipment well known to the chemicalindustry. The

protein is at no time in solution, and the process consists of a seriesof mechanical or physical rather than chemical separations. The resultis that the protein product prepared according to this invention can beproduced at a cost substantially below those of comparable commercialprotein products such as glue, casein, treated vegetable proteins andthe like. in making possible this low cost is the excellent yieldsobtained by our processes. An analysis of average soy bean meal obtainedby extraction of oils shows a content of 45.6 per cent of insolubleprotein. We find recovery of 90 per cent or more entirely feasible, ayield not obtainable in the alkaline extraction-digestion treatmentheretofore used in the manufacture of treated vegetable proteins.

The efiiciency of our mechanical separating step is indicated by thefact that careful burring and screening allows us to consistentlyprepare a protein containing between 0.75 and 0.25 per cent of fibrousand insoluble galactanous material. By the use of extreme care and bynumerous repetitions of the separating step, it is possible to prepare aprotein containing even less than 0.25 per cent of fibrous and insolublegalactanous material. This product is a substantially pure, chemicallyunchanged protein. However, a product containing the fractionalpercentage of fibrous and insoluble galactanous material above indicatedis entirely satisfactory for practical purposes. It may easily be putinto solution by the method described in our co-pending application,Serial No. 192,966, to yield a homogeneous dispersion of low viscosity.

The advantages realized by the use of the novel processes disclosedhereinbefore are particularly apparent when processes on the order ofthose disclosed in United States Patent No. 1,955,375 are considered.Processes of this type involve the selective extraction and digestion ofproteins. Two disadvantages attend this extraction. The first relates tothe fact that a part of the insoluble protein is rendered soluble, andhence lost, by hydrolysis due to the long alkaline treatment necessaryfor complete extraction. The second refers to the fact that theinsoluble, non-proteinogenous residue forms a sticky sludge, from whichit is extremely difiicult to separate the protein containing liquorefiiciently. Hence a loss occurs at this point as well. The treatedvegetable protein obtained by these processes is a fiber-freedrastically hydrolyzed product, typifying all prior art treatedvegetable proteins.

When our novel chemically unchanged vegetable protein containing lessthan 0.75 per cent of fibrous and insoluble galactanous material iscompared with treated vegetable proteins,in paper coating work, by beingput in solution according to the methods disclosed in our copendingapplication Serial No. 192,966, it is found to be equal to the prior artcomposition in pick tests, smoothness, and brightness, and superior asto brushability, printability, and strength. The last fact may also bedifferently stated by saying A substantial factor that the use of moretreated vegetable protein per pound of clay than of our novel protein isrequired to obtain equal strength in coated paper sheets. The reason forthis fact is apparent on consideration of the drastic hydrolysis withconsequent molecular breakdown and lower adhesive strength which forms astep in the processes heretofore used for the production of treatedvegetable proteins. This drastic hydrolysis has heretoiore beennecessary to secure low viscosity and Protein prepared according to thedetailed directions in the specific example described hereinabove may beput into solution by the method described in our co-pending application,Serial No. 192,966. From the resulting solution there may be prepared acoating color containing 16 parts by weight of protein per 100 partscoating clay and having a total solid content of 40 per cent at aviscosity of 200 centiposes. This coating color brushes well and gives apick of 8 when coated at 15 pound coat weight on No. 4 book P p? Whentested in a commercial mill run, a coating color prepared as disclosedin said example using 14.1 parts of protein per 100 parts of clay gave apick of 6.5, the same value as that obtained by the use of a commercialcoating color similarly prepared from casein and tested during the samemill run and on the same raw stock, while in the K and N ink test thenovel Our invention, in its broader aspects, may be said to include theisolation of unchanged protein by purely physical means. Thelatter-include the step of utilizing the differences in size, shape andgravity of particles as between protein and fibrous and insolublegalactanous materials which may be produced by suitable comminution ofdefatted oleaginous vegetable material which has been subjected to aleaching with acidulated water. We are aware that numerous details ofthe process may be varied through a wide range without departing fromthe principles of this invention, and we, therefore, do not purposelimiting the patent granted hereon otherwise than necessitated by thescope of the appended claims. 1

We claim as follows: v

1. The process of isolating the protein of oleaginous seed materialwhich includes comminuting and defatting said seed material, steepingand washing the seed material in water to remove water soluble material,burring the washed material in the presence of water to the extent ofproducing rounded protein particles and fibrilliform particles offibrous and galac tanous material, screen ofi the flbrilliform particlesin the presence of water to prepare an aqueous protein suspension,settling the protein from said suspension, and separating the settledprotein, the water used in said steeping, washing, burring, screening,suspension and settling being acidulated and approximately at theisoelectric point of the protein isolated.

2. The process of isolating the protein of soya bean which includescomminuting and defatting soya bean, steeping and washing the resultingmaterial in water to remove water soluble material, burring thecomminutddefatted, washed material in the presence of water to reducethe same to fibrilliform particlesof fibrous and galactanous materialand to rounded protein particles capable of being separated from thefibrilliform particles by wet-screening and of settling from an aqueoussuspension, screening the burred material in the presence of water toremove fibrous and galactanous material and to prepare an aqueoussuspension of protein particles, settling the protein particles, andseparating the settled protein particles, all water contacting said soyabean material insaid process being acidulated and having a pH of from3.8 to 5.4.

3. The process of isolating the protein of soya bean which includescomminuting and defatting soya bean, steeping and washing the resultingmaterial in water to remove water soluble material, burring thecomminuted, defatted, washed material in the presence of water to breakup protein agglomerates and to set free individual rounded proteinparticles capable of settling from an aqueous suspension and to causefibrous and galactanous material to string out in the form of longfibrils, screening the burred mate rial to remove fibrilliform fibrousand galactan-, ous material and to leave an aqueous suspension ofprotein particles, settling the protein particles and filtering ofi anddrying the settled protein particles, all the water used in said processhaving a pH approximating the isoelectric point of said protein.

JOHN C. BRIER. 'GERARD W. MULDER.

